Ferrite switching circulators can be used to implement downlink beam hopping techniques in multibeam broadband satellite systems, where a single high power RF input can be quickly switched to multiple output antennas. A single 3-port ferrite circulator switch, although simple to implement, compact and relatively inexpensive, has a downside in that if a short or open circuit occurs within a connected output port, or if an output port is not properly connected, then radio frequency (RF) power can be reflected back into the switch. This reflected power can travel back through the circulator, exit another port of the circulator, and energize equipment that should have remained de-energized. To provide isolation between switched output ports, designs have been introduced comprising a configuration of three multifunction waveguide ferrite circulators (sometimes referred to as a ferrite circulator “triad”) which include three ferrite junction switches and two high power loads. In a triad design, one of two high power loads is coupled to a first circulator while the other high power load is coupled to a second circulator. The input to a third ferrite circulator is switched between two outputs, where the first output is coupled to the input of the first ferrite circulator, and the third circulator's second output is coupled to the input of the second circulator. In such a triad design, if a short circuit occurs on a connection to the output port of the first ferrite circulator, then the reflected RF power is reflected back into the circulator and directed to its high power load which serves to absorb the reflected RF power. Similarly, the high power load coupled to the second circulator will receive and absorb reflected RF power received back in from the output port of the second circulator. Since minimal reflected RF power is transmitted back to the third circulator, isolation between the two output ports of the triad is achieved.
In order to improve satellite throughput in satellite communications, specified RF power levels used by satellites have been on the rise. The increases in RF power level may come either through improvements in output power of the on-board high power transmitters or through the combining of several high power transmitters. For this increase in RF power level, the limitation in the triad switches is the power handling of the ferrite switches and high power loads. That is, the high power loads used by the triad switches need to be able to handle the full transmit power levels (which can be on the order of 50 to 500 watts, for example) in case of a short circuit at an output to the switch. The high power loads need to be capable of absorbing the full reflected input power, which typically translates into the need for the high power loads to be larger and heavier. In the design of satellite systems, however, the space available within the satellite is typically a premium resource, and any extra weight has a direct detrimental effect in the cost associated with launching the satellite into orbit.
For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the specification, there is a need in the art for improved systems and methods for improved ferrite circulator RF power handling.